1. Field of the Invention
The present invention is directed to a lift tube for an agricultural implement frame wherein the lift tube is covered with a sleeve of corrosion resistant material.
2. Description of the Prior Art
In recent years, the transverse working width of towed agricultural implements has increased so that the farmer can cover more area in a single pass. Although this increased transverse width has greatly increased farmer efficiency in field operations, it does present a problem in transporting the implement from one field to another, along roads and through fence gates. To overcome this transport problem, the implement needs to be folded into a more compact transport configuration.
Most relevant here, some row crop planters have been marketed with agricultural implement frames comprising a carrier frame and a main frame. The carrier frame has a transverse working position and a longitudinal transport position. The carrier frame is lifted relative to the main frame from its transverse working position and pivoted into a longitudinal transport position. In one embodiment, the carrier frame is lifted on a lift tube, see U.S. Pat. No. 5,346,019. The lift tube of this frame is provided with stainless steel corners that are welded to a main support tube. It is also known to sheath the posts with stainless steel sheets that are plug welded to the underlying tube and butt welded at the corners. Use of stainless steel is desirable to reduce corrosion. Corrosion resistance is desired to reduce wear on the nylon pads that slide up and down the tube and to maintain the desirable appearance of the tube. This is particularly true when the tube is exposed to corrosive liquids, such as liquid fertilizer.
It is an object of the present invention to provide a lift tube for a lift and rotate agricultural implement frame, wherein the lift tube is provided with a sleeve of corrosion resistant material.
It is a feature of the present invention that the sleeve is formed from stainless steel plates that are welded to one another and to the main support tube by fillet welds.
A lift and rotate agricultural implement frame comprises a main frame having a lift tube and a carrier frame slidably mounted to the lift tube, so that the carrier frame can be lifted vertically relative to the main frame. The lift tube comprises a vertically extending main support tube and a corrosion resistant exterior sleeve. The main support tube comprises a plurality of vertically extending planar surfaces. The corrosion resistant exterior sleeve comprises a plurality of vertically extending corrosion resistant plates corresponding to the planar surfaces of the main support tube. Each of the plates has an interior surface adjoining the corresponding planar surface of the main support tube and an exterior surface that adjoins a bearing plate mounted to the carrier frame. At least one of the corrosion resistant plates adjoins another plate. One of the adjoining plates is provided with an overhang that extends past the exterior surface of the other plate. The plates are fillet welded to one another between the overhang and the other plate.
In the illustrated embodiment, the main support tube is square and has four planar surfaces. Similarly the sleeve is also square and formed from four vertically extending plates. Each of the plates has an overhang extending over an adjacent plate. A fillet weld is made between the overhang and the adjacent plate to join the plates together. The plates are also provided with oblong openings having oblong edges. The oblong edges are fillet welded to the main support tube to couple the sleeve to the main support tube.
The square main support tube could also be encased by a sleeve having two plates. Both plates could be bent at ninety degrees with the first plate overhanging the second plate at one corner and the second plate overhanging the first plate at the opposite corner. It is also possible to form the sleeve from one plate having three ninety degree bends. With one plate, one of the vertical edges of the plate would overhang the other vertical edge and the vertical edges would be fillet welded to one another.
The welds joining the sleeve to the main support tube is removed from the bearing area. This reduces the amount of weld spatter that needs to be removed to prevent damage to the nylon bearing pads. At the corners, fillet welds are easier to make than butt welds. Fillet welds can be made by seam tracking with a robotic welder. In addition, fillet welds are more tolerant of variations in sheet width than butt welding.